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.Dd August 29, 2025
.Dt GROUP 5
.Os
.Sh NAME
.Nm group
.Nd format of the group permissions file
.Sh DESCRIPTION
The
.Nm
file is the local source of group information.
It can be used in conjunction with the Hesiod domain
`group', and the NIS maps `group.byname' and `group.bygid',
as controlled by
.Xr nsswitch.conf 5 .
.Pp
The file
.Nm
consists of newline separated
.Tn ASCII
records, one per group, containing four colon
.Ql \&:
separated fields.
These fields are as follows:
.Bl -tag -width password -offset indent -compact
.It group
Name of the group.
.It passwd
Group's
.Em encrypted
password.
.It gid
The group's decimal ID.
.It member
Group members.
.El
.Pp
Lines whose first non-whitespace character is a pound-sign (#)
are comments, and are ignored.
Blank lines that consist
only of spaces, tabs or newlines are also ignored.
.Pp
The
.Ar group
field is the group name used for granting file access to users
who are members of the group.
The
.Ar gid
field is the number associated with the group name.
They should both be unique across the system (and often
across a group of systems) since they control file access.
The
.Ar passwd
field
is an optional
.Em encrypted
password.
This field is rarely used
and an asterisk is normally placed in it rather than leaving it blank.
The
.Ar member
field contains the names of users granted the privileges of
.Ar group .
The member names are separated by commas without spaces or newlines.
A user is automatically in a group if that group was specified
in their
.Pa /etc/passwd
entry and does not need to be added to that group in the
.Nm
file.
.\" .Pp
.\" When the system reads the file
.\" .Pa /etc/group
.\" the fields are read into the structure
.\" .Fa group
.\" declared in
.\" .In grp.h :
.\" .Bd -literal -offset indent
.\" struct group {
.\"	char    *gr_name;        /* group name */
.\"	char    *gr_passwd;      /* group password */
.\"	int     gr_gid;          /* group id */
.\"	char    **gr_mem;        /* group members */
.\" };
.\" .Ed
.Sh IMPLEMENTATION NOTES
The
.Xr passwd 1
command does not change the
.Nm
passwords.
The
.Xr pw 8
utility's
.Cm groupmod
command should be used instead.
.Sh LIMITS
There are various limitations which are explained in
the function where they occur; see section
.Sx SEE ALSO .
.Pp
In older implementations,
a group cannot have more than 200 members.
The maximum line length of
.Pa /etc/group
is 1024 characters.
Longer lines will be skipped.
This limitation disappeared in
.Fx 3.0 .
Older binaries that are statically linked, depend on old
shared libraries, or
.No non- Ns Fx
binaries in compatibility mode
may still have this limit.
.Sh FILES
.Bl -tag -width /etc/group -compact
.It Pa /etc/group
.El
.Sh SEE ALSO
.Xr newgrp 1 ,
.Xr passwd 1 ,
.Xr setcred 2 ,
.Xr setgroups 2 ,
.Xr crypt 3 ,
.Xr getgrent 3 ,
.Xr initgroups 3 ,
.Xr nsswitch.conf 5 ,
.Xr passwd 5 ,
.Xr chkgrp 8 ,
.Xr pw 8 ,
.Xr yp 8
.Sh HISTORY
A
.Nm
file format appeared in
.At v6 .
Support for comments first appeared in
.Fx 3.0 .
